flex中关于文件的的添加和删除问题

<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009" 
					   xmlns:s="library://ns.adobe.com/flex/spark" 
					   xmlns:mx="library://ns.adobe.com/flex/mx">
	<fx:Declarations>
		<!-- 将非可视元素（例如服务、值对象）放在此处 -->
	</fx:Declarations>
	<fx:Script>
		<![CDATA[
			import flash.events.Event;
			import flash.filesystem.File;
			import flash.filesystem.FileMode;
			import flash.filesystem.FileStream;
			
			import mx.controls.Alert;
			
			private var outputFolderFile:File = new File();
			private var strFile:File;
			private function saveHandler(event:MouseEvent):void
			{
				outputFolderFile.browseForDirectory("Select Directory");
				outputFolderFile.addEventListener(Event.SELECT,directorySelectedHandler);
			}
			private function directorySelectedHandler(e:Event):void
			{
				strFile = outputFolderFile.resolvePath("李虎.txt");
				saveWritedUtfBytes(strFile,taStr.text);
			}
			public function saveWritedUtfBytes(file:File,data:String):void
			{
				try{
					var fileStream:FileStream = new FileStream();
					fileStream.open(file,FileMode.WRITE);
					fileStream.position = 0;
					fileStream.writeUTFBytes(data);
					fileStream.close();
					taStr.text="";
				}catch(e:Error){
				trace("字符串写入失败");
				}
			}
			
			private function deleteHandler(evt:MouseEvent):void
			{
				if(strFile.exists);
				{
					strFile.deleteFile();
					Alert.show("删除成功！");
				}
				
			}
		]]>
	</fx:Script>
	<s:VGroup top="10" left="10">
		<s:Label text="请输入一串字符:"/>
		<s:TextArea id="taStr" width="200"/>
		<s:Button width="80" height="30" label="保存" click="saveHandler(event)"/>
		<s:Button width="80" height="30" label="删除" click="deleteHandler(event)"/>
	</s:VGroup>
	
</s:WindowedApplication>